The dispensing of liquid chemical products from one or more chemical receptacles is a common requirement of many industries, such as the laundry, textile, ware wash, healthcare instruments, and food processing industries. For example, in an industrial laundry facility, one of several operating washing machines will require, from time to time, aqueous solutions containing quantities of alkaloid, detergent, bleach, starch, softener and/or sour. Increasingly, such industries have turned to automated methods and apparatus systems for dispensing chemical products. Such automated methods and apparatus systems provide increased control of product use and reduce human contact with potentially hazardous chemicals.
Contemporary automatic chemical dispensing systems used in industry rely on pumps to deliver the liquid chemical products from a storage container. Generally, these pumps deliver raw product directly to a machine for use or to a dilution manifold or container where the product is mixed with a diluent, typically water. Such systems are relatively simple in concept, but they can be expensive to build and operate. A number of methods for the control of dispensing these chemical products have been developed and employed and are well known in the art.
In many contemporary chemical dispensing systems, the chemical products are stored in containers and probe assemblies are used to monitor the level of the product in these containers. One common type of probe assembly includes two probes separated by a distance so that the probe assembly has a high input impendence when exposed to air. Because the products are typically conductive, the input impendence of the probe assembly is lower when the probes are in contact with the product. To provide an indication of the level of product in a container, the probe assembly is mounted in the container so that the probes are in contact with the product when the container is sufficiently full. When the level of product drops below the probes, the probes are exposed to air, increasing the input impedance of the probe assembly. To notify the operator of the chemical dispensing system that the container is running low on product, a monitoring device is connected to the probe assembly. In this type of detection system, the monitoring device is configured to detect the increase in the input impedance of the probe assembly, and may thereby notify an operator that the product is about to run out by providing an alarm.
The operator may be responsible for multiple chemical dispensing systems, each of which will typically be located remotely from the operator's workspace. In addition, the machines connected to each of the chemical dispensing systems may require several different chemical products in order to perform properly. The monitoring system will therefore typically include multiple probe assemblies and monitoring devices so that each of several containers containing different chemical products is individually monitored. Thus, a typical monitoring system may require several cable runs from multiple locations in order to provide full coverage of all the containers the operator is responsible for maintaining. Increasing the number of containers and locations that must be monitored will further result in increased cabling requirements. This large number of cable runs will increase the complexity and expense of the monitoring system, and may also reduce the monitoring system's reliability due to the increased number of connections and potential failure points.
Further reliability issues may arise from use of conventional probe assembly designs. Because the aforementioned level monitoring systems rely on the measured input impedance of the probe assembly to detect the level of the product, anything that affects this measurement can have a negative impact on the reliability of the system, Probe assemblies may experience reliability issues over time from the product attacking the probes due to the corrosive nature of many of the chemicals typically found in the product. Even when the probes utilize resilient types of materials such as stainless steel or graphite, the probes are generally being electrically charged by the monitoring device in order to measure the capacitance or input impedance of the probe assembly. This electrical charge may result in electrolysis occurring at the electrodes, which will tend to foul even a chemically resistant material after a sufficient period use. The product may also be sufficiently viscous so that the product clings to the probes or leaves a semi-dried residue, causing the probes to indicate that sufficient product is present in the container after the level of the product has dropped below the probes.
Fouled or otherwise compromised probe assemblies and/or monitoring devices may cause erroneous readings. These erroneous readings may result in false alarms and/or failures to notify the operator that a product is running out. These errors can be addressed by performing continuous maintenance of removing and cleaning the probe assembly, undesirably increasing operational expenses. False alarms may result in unnecessary trips to refill a container that already contains sufficient product, which also increases operating expenses. Frequent false alarms may also cause operators to either ignore or disconnect the monitoring system, increasing the likelihood that a container running low on product will go unnoticed.
Large numbers of cables and compromised probe assemblies may thus collectively reduce the reliability and increase the cost of chemical product level monitoring systems. For the aforementioned reasons, unreliable monitoring systems may result in machines attached to the chemical dispensing system running without the required amounts of the chemical products being dispensed. The performance of the machines fed by the chemical dispensing system may thereby be adversely affected due to too little of the product being dispensed, reducing the quality of machine's output and increasing expenses by requiring goods to be re-processed through the affected machine.
Therefore, there is a need in the art for improved monitoring system components and methods that more accurately and reliably detect the presence of chemical products over time for use with chemical dispensing systems.